A satellite communication system includes one or more satellites serving as a relay station for two or more stations, or user terminals, on or near the earth. The satellite communication system can provide two-way communication or communication links among user terminals, with one central hub and many remote stations.
The bandwidth available for the transmission from a user terminal to a satellite, or an uplink, and from the satellite to the user terminal, or a downlink, will depend on the frequency band used by the satellite communication system. Higher frequency bands such as the Ku band of 14.0-14.5 GHz for uplink and 10.7-12.75 GHz for downlink, Ka-band of 27.5-31 GHz for uplink and 17.7-21.2 GHz for downlink, V-band of 47.2-50.2 GHz for uplink and 37.5-42 GHz for downlink provide a wide bandwidth of up to 4.5 GHz spectrum. Typically, a single satellite will handle a large bandwidth and divide it into a number of channels of smaller bandwidth.
A satellite communication system must be tailored to particular application demands. For example, military wideband communications require sufficient capacity for enabling execution of tactical command and control, intelligence, surveillance and reconnaissance, battle management and combat support information. Currently, military wideband communications are supported by: the Defense Satellite Communication System (DSCS) that operates in the X-band; the Global Broadcast Service (GBS) that operates in the Ka-band; and commercial satellites operating in the C and Ku-bands. A Wideband Gapfiller Satellite (WGS) will replace the DSCS and GBS in the future. The WGS operating in X-band and military Ka-band will have 19 independent beams that can be positioned throughout the field of view of each satellite.
In order to satisfy military demands for increasingly higher bandwidth to support high data rate users, satellites must be continuously placed in service to maintain the needed capacity. However, problems associated with the military procurement process such as, for example, long development times, funding and schedule slip result in delayed service starts.
Servicing of commercial satellites does not involve many of the problems discussed above. Therefore, commercial satellites can be used to augment present military capacity. However, typical commercial satellite communication systems are optimized to focus resources on large population centers. That is, the commercial satellite communication systems operate with fixed beams having limited coverage in the open ocean and sparsely populated areas of the earth and have limited channel bandwidth. Further, commercial satellite communication systems typically operate in the C and Ku band and have limitations in supporting Department of Defense (DoD) requirements where and when needed.
Military wideband communications, on the other hand, require flexible satellite communication systems in which capacity and connectivity can be redirected to areas anywhere within the satellite field-of-view where military related operations are needed.